Value-entering mechanism

ABSTRACT

A plurality of series of ordinally arranged depressible value keys, each ordinal row of keys being effective to control a differential adjustment of a corresponding value selection slide in accordance with the selective depression of a value key. An interponent for each key is rocked by the selective depression of a key in a given row of keys to adjust a latch-releasing slide controlling the movement of a latch member from an active to an inactive position. When moved to its inactive position, the latch member enables the differential adjustment of a corresponding selection slide under the influence of a spring and in accordance with a value key depressed. Thereafter, the latch member retains a latch-releasing slide in its adjusted position, locking the depressed key in its depressed condition, and preventing depression of the other keys in the corresponding row of keys. The latch member and latch-releasing slide are returned to their initial positions upon power restoration of the adjusted selection slide.

United States Patent [72] Inventors [5 4] VALUE-ENTERING MECHANISM 10 Claims, 6 Drawing Figs.

[52] US. Cl 235/101, 235/27, 235/145 [51] Int. Cl G07g 1/00, G060 7/02 [50] Field ofSearch 235/145,

[56] References Cited UNITED STATES PATENTS 2,495,832 l/l950 Boyden 235/145 2,812,138 11/1957 Malavazos 235/145 Primary Examiner-Stephen J. Tomsky Assistant Examiner-John F. Gonzales AttorneysPatrick .l. Schlesinger, Charles R. Lepchinsky and Jay M. Cantor ABSTRACT: A plurality of series of ordinally arranged depressible value keys, each ordinal row of keys being effective to control a differential adjustment of a corresponding value selection slide in accordance with the selective depression of a value key. An interponent for each key is rocked by the selective depression of a key in a given row of keys to adjust a latch-releasing slide controlling the movement of a latch member from an active to an inactive position. When moved to its inactive position, the latch member enables the differential adjustment of a corresponding selection slide under the influence of a spring and in accordance with a value key depressed. Thereafter, the latch member retains a latchreleasing slide in its adjusted position, locking the depressed key in its depressed condition, and preventing depression of the other keys in the corresponding row of keys. The latch member and latch-releasing slide are returned to their initial positions upon power restoration of the adjusted selection slide.

PATENTEDMAR] 61971 34570158 sum 1 OF 2 INVENTORS, CECIL F. CLEMONS GEORGE C WU QIATHANI L F.

HAWT o as M Wwi ATTORNE BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to postage meters and more particularly to a selection mechanism wherein a value is entered and is thereafter printed as a part of the indicium while being subtracted from the prepaid postage register. The entry of the value is under the control of selectively settable members which may be in the form of rockable levers or depressible keys.

2. Description of Prior Art In prior art meters utilizing full keyboards, a depressed key releases a corresponding selection slide or rack, which key, when latched depressed, provides a stop for the differential adjustment of the slide. The key depression is so sensitive that the slightest pressure on a value key is effective to release the value selection slide. To often, such a depression is not sufficient to enable the key to be latched in its depressed position. In this situation, the selection slide is released for its full extent of movement, i.e., for the entry of a value of l in any one or all of the keyboard orders. Should an operator neglect to note that the key or keys did not latch depressed and the meter operation was initiated, an erroneous postage value would be impressed on the mail matter and subtracted from the prepaid postage. Such errors in a setting up of values in the keyboard can be costly to the user whether it be in the lowest order or the higher orders.

According to the present invention, this and other problems of the prior art are overcome by a value-entering mechanism that includes ordinally arranged selection slides which are differentially adjustable to represent a value. Also, ordinally arranged value keys are selectively depressible to control the differential adjustment of the corresponding slides and a latch means for each selection slide is normally operative to retain the slides in the inactive position. A latch-releasing means is actuated by a selected key in a given row of keys operable to release the corresponding selection slide, to retain the value key depressed and to prevent depression of a value key other than the depressed key in the corresponding row.

SUMMARY OF THE INVENTION More specifically, the latch-releasing means may include a toggle linkage employed to maintain a selection slide latched in its inactive position. Upon a partial or complete depression of a value key rather than a slight depression or tapping of the key, the toggle is broken, releasing the selection slide to the influence of a spring. Immediately, the slide, during its movement, completes the depression of a key through an interponent associated with each key. With the operation of the toggle and the movement of the selection slide, the selected value key is always fully depressed to provide a stop for the differential adjustment of the slide in accordance with the value of the depressed key.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages will be apparent from the following description of a preferred embodiment as illustrated in the accompanying drawings in which:

F l6. 1 is a fragmentary sectional elevational view of the meter, showing the value selection mechanism;

PEG. 2 is a plan view of the value selection mechanism showing the ordinal selection slides and the keyboard with portions broken away to reveal the various components;

FIG. 3 is an elevational view of the rearward end of the keyboard assembly, the view being taken on the plane indicated by line 3-3 in H6. ll;

Fit 4 is a fragmentary elevational view of a selection slide latch mechanism;

FlG. 5 is a fragmentary elevational view of a single keyboard order showing a selection slide in a differentially adjusted position; and

HQ. 6 is a view of the dollar lock key.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention, as described herein, is preferably shown as embodied in a postage-metering machine of the type disclosed in the copending application of John F. Reus, et al. Ser. No. 725,006, filed Apr. 29, 1968, now U.S. Pat. No. 3,526,358. In the use of postage meters of this kind, postage values entered in the keyboard, by the selective depression of value keys, is caused to be printed on mail matter as a part of the indicia with each meter operation. At the same time, the keyboard value is registered in the ascending register and descending register, each of which registers is shown in phantom line in F IG. 2, and generally indicated at If) and i2, respectively.

The keyboard, generally indicated at 14- (FIG. 1) is comprised of four ordinal rows of nine value keys 15, each representative of values of from 1 to 9, i.e., a tenths of cents, or mills, order, a units of cents order, tens of cents order and a hundredths, or dollar, order. Associated with the keyboard 14 is a series of value selection slides, or racks, 16 (FIGS. 1 and 2) one such slide 16 for each ordinal row of keys. Upon depression of a value key 15, a corresponding selection slide 16 is differentially adjusted in accordance with the value of the key depressed to control adjustment of the type wheels in the print head and the registration of the value in the ascending and descending registers, as described in the aforementioned application.

Upon the selective depression of a value key 15, the lower end extremity of the key extends below the keyboard frame and a movement is imparted to a shuttle, or slide, 17 which becomes effective upon such movement, to latch the depressed key in its depressed condition and to prevent depression of other keys in the same ordinal row of keys. lmmediately upon movement of the shuttle 17 by the depressed key 15, a toggle linkage, generally indicated at 18 (FIG. I and 5), is broken, moving a latch plate 19 from a normally active to an inactive position. Upon such movement of the latch plate l9, the corresponding ordinal selection slide R6 is released to the influence of its spring, whereupon the appropriate one of a plurality of stop members on the selection slide engages the extended lower end of the depressed key E5 to control a differential movement of the slide in accordance with the value of the key depressed. Upon the differential adjustment of each of the selection slides 16, the value represented by the depressed key 15 is indicated in the corresponding dial 20 (FIG. 2). To this end, the rack portion of the differentially adjusted slide 16 is enmeshed with a pinion 21 (FIG. l), which, in turn, is enmeshed with a gear 22 for imparting angular rotation to the dial 20.

Each series of nine value keys 15 representative of the values from 1 to 9 is ordinally arranged within a keyboard framework comprising a lower frame member 26 in the form of a channel and a top keyboard plate 27 (PEG. 3). The channel member 26 is supported between a pair of parallel plates 2% by any suitable means such as, for example, a plurality of screws 29. At their respective ends, the plates 28 are secured to the meter frame members 30 and 31. The top plate member 27 of the keyboard structure is secured in place on the channel member 26 by a plurality of screws 32.

inasmuch as each ordinal row of keys and associated mechanism is identical, it is believed that a description of one order, for example, the tenths of cents, or mills, order will suftice. Each of the value keys 15 includes a keytop 33 (FIGS. 1 and 5) secured on the upper end of a keystern 34 slidably supported for endwise movement in the channel member as and keyboard top plate 27. Normally, the keys in each ordinal row of keys are resiliently urged upwardly by means of a longitudinally extended coil spring 35 to retain projections 36 (FIG. 3) on each keystem 34 in engagement with a lock plate 3'7. Lock plate 37 is positioned adjacent the underside of the top plate 27 and is maintained in spaced relation to channel member 26 by spacers 38 through which screws 32 are passed. At its lower end, each keystem 34 is provided with an extension of a reduced width with respect to the upper portion of the keystem. This lower extension 42 of alternate keys in each row of keys (FIGS. 2 and 3) is oppositely offset relative to the adjacent keys and is adapted, upon depression of a key, to differentially limit the movement of the corresponding selection slide 16.

Each of the selection racks, or slides, 16 is provided with a series of stop members, one for each of the keys in a cor responding ordinal row of keys. Each of the stop members 13, 44,, 45, 46 and 47 extend upwardly (FIGS. 1 and 2) having their end portion formed over at a right angle thereto and disposed in a common plane parallel to the channel member 26 of the keyboard 14. These stop members are adapted for cooperation with the extension 42 of the keystems 34 of value keys l, 3, 5, 7 and 9, respectively, upon the selective depression of each key. Each selection slide 16 is also provided with alternately disposed stop members 48, 49, 59 and 51, which are laterally offset with the upwardly extended end portion disposed in a common plane parallel to the plane of movement of the slide, and are adapted to engage the extension 42 of the keystems 34 of respective depressed value keys 2, 4, 6 and 8.

Each of the selection slides 16 (FIGS. 1 and 2) is normally urged to the left from a normally latched position by means of a relatively strong spring 55. Selection slide 16 in the tenths of cents order is mounted for endwise movement upon the lower sideplate 28 (FIG. 2) by means of pins 56 on the plate 28 engaged in slots 57 of the rack (FIG. 1). Similarly, the selection slide 16 associated with the units of cents order is mounted for endwise movement on a support plate 58, secured at its respective ends to end frame member 31 and auxiliary frame member 59 (FIG. 2). The selection slide 16 associated with the tens of cents order is supported for endwise movement similarly to that of the units of cents rack, or slide 16, while the selection slide 16 of the hundredths, or dollar, order is supported for endwise movement on the upper sideplate 28, as viewed in FIG. 2.

Associated with the selection slides 16 are a series of latching plates 19, one such plate for each slide, rockably mounted at one end of the selection slide-supporting pin 56 between the selection slide and its supporting plate (FIGS. 1, 2, 4 and 5). With each plate 19 is an elongated slot 60, the right-hand end portion of which is formed angularly upwardly, as seen in FIGS. 1 and 5. In the normal latching position of the latch plate 1.9, as seen in FIG. 1, a roller 61 is disposed in the upwardly angularly formed end of the slot 69. Roller 61 is carried by an arm 62, intermediate its ends, which arm 62 is pivotally supported at 63 on the left end of the selection slide 16 (FIG. 5 or on the right end of the slide as viewed in FIG. 4. At its lower end, arm 62 carries a pin 64 supporting one end of a spring 65, the other end of which is supported on a pin 66, carried on selection slide 16 (FIG. 5).

When latch plate 19 is in normal counterclockwise-rocked position shown in FIG. l and the roller 61 is in the upwardly angularly extended portion of the slot 60, the corresponding selection slide 16 is latched against movement, under the influence of its spring 55. However, upon rocking latch plate 19 in a clockwise direction (FIGS. 1 and 5), the associated selection slide 16 immediately moves to the left (FIG. 5) a differential extent in accordance with the value key depressed and the roller 61 moves in a horizontal plane along the elongate portion of the slot 60.

Rocking of the latch plate 19 from the normally active position shown in FIG. 1, to the inactive position shown in FIG. 5, is under the control of the toggle linkage 18. The toggle linkage 18 includes a three-arm bellcrank 7i) pivotally supported at 71 on and adjacent sideplate 28. The other member of the toggle linkage 18 is connecting link 72, which is pivotally connected at its one end to one arm of bellcrank 7t} and at its other end by a pin and slot connection 74 to the upwardly projected ear of latch plate 19. The second arm 73 of the threearrn bellcrank 79 is arcuately formed to engage the rounded end of the latch plate 19 which serves as a limit for the bellcrank 70, upon clockwise rocking movement thereof. as seen in FIG. 5. In the active position of the latch plate 19 and the locking position of the toggle linkage 18, the pivotal connection of the link 72 with the one arm of the bellcrank is below a hypothetical centerline through the pivotal pin 71 and the pin and slot connection 74 In this position of the parts, the lower flat edge surface of the one arm of bellcrank 70 engages the shoulder 75 of latch plate 19. A third arm 76 of bellcrank 70 is angularly disposed to the left, as seen in FIG. 1, with bellcrank 79 in its locking position. At its upper end, the arm 76 is provided with a spherical segmental head 77 engaged in a suitable notch 78 provided in an auxiliary plate 79 secured to the outer surface of one flange of the key-controlled shuttle, or slide, 17.

Each of the ordinal slides 17 is in the form of a channel and is supported for endwise movement on the lower keyboard frame member 26 guided in the movement by pins 80 (FIG. 2) carried by each slide 17, adjacent the forward and rearward ends thereof, and engaged in suitable elongated slots in the frame member 26. Normally, each of the slides, or shuttles I7 is biased to the left as seen in FIGS. I, 2 and 5 by a spring, similar to the spring 84 associated with the topmost, or hundredths order, slide 17 in FIG. 2, which spring 84 is supported at its one end on a pin 85 secured to a flange of the slide 17 and at its other end is supported on a pin 86 secured to the lower frame member 26.

In order to control the movement of each slide 17, a plurality of rockable balls 87 are provided, one for each value key 15 in each ordinal row of keys. These bails 87 are rockably supported on transverse shafts 88 secured at their respective ends in sideplate members 28 as seen, for example, in FIG. 3). One leg 89 of each substantially U-shaped ball 87 is in the form of a circular segment (FIGS. 1 and 5) having a radial extension, the circular end portion 91) of which is engaged in a suitable slot 91 (FIG. 2) in the corresponding shuttle, or slide, 17. Suitable slots in the lower frame member 26 are provided and are in registry with each of the slots 91 in the channel slide 17, such slots enabling the rocking motion of the bails 87. The other leg 92 of each of the substantially U-shaped bails 87 is in the form of a cam, a larger radial .portion of which is provided with a notch 93 in the peripheral surface thereof, adapted for engagement by a tooth, or projection 94 on a corresponding keystem M.

It can readily be seen that upon the selective depression of a key in a given ordinal row of keys as, for example, the 5 value key 15 in the tenths of cents order (FlG. 5), the tooth 94 on the keystem 34 engages notch 93 in the arm 92 of the corresponding bail 87. Thus, upon depression of the key, the bail 87 is rocked counterclockwise to the position shown in FIG. 5, moving the corresponding slide 17 to the right, whereupon each of the bails 87 in the same ordinal row of keys are likewise rocked and serve to prevent depression of any of the other keys in the row of keys. This comes about by the rocking of the arcuate portion 95 of the bails 87 into blocking relationship with respect to the tooth 94 of the associated key 15. Upon complete depression of the 5 value key 15, and the adjustment of the slide 17 to the right, as seen in FIG. 5, the corresponding selection slide, or rack, 16 is released, moving to the left in FIG. 5 until the stop 45 engages the lower end of the depressed key 15.

Referring to FIG. 1, it will be noted that there is a lost motion between the left-hand edge of the notch 73 and the end portion 77 of the arm 76 of bellcrank 70. This pennits the projection 94 of each key, as it is depressed, to rock the corresponding bail $7 sufficiently for the projection to engage in the notch 93 prior to the release of the corresponding selection slide 16. Because of this lost motion, a selection slide can never be released by a very slight depression or tapping of a key.

In order to effect the release of the selection rack 16, the adjustment of the tenths of cents ordinal shuttle 17 to the right in FIG. 5 rocks bellcrank 70 clockwise to impart a slight clockwise rocking motion to the associated latching plate 19. Such motion of the latch plate 19 is sufficient to enable the tenths of cents ordinal selection slide 16 to be released immediately to the influence of its relatively strong spring 55,

whereupon the corresponding roller 61 moves along the elongated portion of slot 60 in the plate 19. Such movement of the slide 16 serves to complete the depression of the key. The length of the elongated portion of the slot 60 is sufficient to enable the selection slide 16 to be moved to the left the full extent of its movement, i.e., to the position representative of the value of 1. While the section slide 16 is in its actuated, or differentially adjusted position, the roller 61, disposed in the elongated portion of the slot 60 of the corresponding latch plate 19, prevents the restoration of the toggle linkage 18 to its normally active position. Thus, the bellcrank 70 of the toggle linkage 18 retains the corresponding ordinal shuttle 17 in its adjusted position, thereby locking the selected key in its depressed condition and blocking depression of the other keys in the same keyboard order.

Upon a differential adjustment of each selection slide 16, a pair of selection gears are likewise differentially adjusted relative to a corresponding stepped tooth actuator drum to effect a registration of the value in the ascending and descending registers, upon operation of the meter. At the same time, a collar associated with each of the selection slides is adjusted to effect the setting of the corresponding-type wheel in the print head inaccordance with the value set in the keyboard. Referring to FIG. 1, for example, a differential adjustment of the tenths of cents ordinal selection slide 16 imparts a similar adjustment to a selection gear control slide 96. Adjustment of the slide 96 becomes effective through a guide member 97, secured thereon to move a collar 98 axially for the adjustment of the corresponding ordinal-type wheel in the meter print head in accordance with the value set in the keyboard, At the same time, a pair of selection gears, similar to gear 105, in P16. 1, are differentially adjusted by the gear control slide 96 relative to a corresponding stepped tooth actuator drum such as drum 106 F 16. 1). With each cycle of operation of the postage meter, the actuator drums o become effective to cause the value to be registered in the ascending register and the descending register, all of which is fully described in the aforementioned copending application, Ser. No. 725,006.

It will be noted that in addition to the value keys 15, the keyboard 14 includes a dollar lock key 107, FIGS. 1 and 6. Key 107 is supported for endwise movement on frame member 31 by the engagement of pins 108 on frame member 31 in elongated slots 109 in the keystem 110. Normally, the dollar lock key 107 is urged upwardly to the position shown in FIG. 6, by a spring 111 and serves to prevent an inadvertent depression of a value key in the hundredths, or dollar, order of the keyboard 14. To this end, the right-hand flange of the shuttle 17 (FIG. 6) associated with the hundredths order of the keyboard is provided with an extension 112. In the normally inactive position of the shuttle 17 (FIGS. 1, 2, 5 and 6), a notch 114 in the extension 112 thereof is adapted to be engaged by a lateral projection 115 on keystem 110. By the engagement of the projection 115 of keystem 110 of the dollar lock key 107 with the notch 114 in the dollar order shuttle 17, depression of the dollar order value keys 15 is prevented. Therefore, when it becomes desirable to enter a dollar value in the keyboard 14, the dollar key 107 must first be held depressed followed by the selective depression of the desired value key 15.

Restoration of each differentially adjusted selection slide 16 to its normally inactive position is controlled in a well-known manner by the rocking of a segmental rack 116 (FIG. 2) which, in turn, imparts rotation to the pinions 21 associated with each of the selection slides as described in the aforementioned application. As each adjusted selection slide is returned to the right (FIG. 5), the roller 61 on the yieldable arm 62 engages the angular portion of the slot 60 when spring 65 (FIG. 4) biases the arm 62 counterclockwise, as viewed in FIG. 5, rocking latch plate 19 in a counterclockwise direction. Upon the counterclockwise rocking movement of the latch plate 19 to its active latching position, the one arm of the bellcrank 70 of the toggle linkage 18 engages the shoulder 75 of the latching plate .39 to lock the selection slide 16 in its normally inactive position. As the toggle linkage 18 is returned to its normal position, the associated shuttle, or slide, 17 returns to its normally inactive position under the influence of its spring 84, thereby enabling the return of the depressed value key 15 to its raised position.

We claim:

1. In a postage meter having a plurality of registers and an actuating means therefore:

a plurality of value selection members ordinally arranged and differentially adjustable from a normally inactive to an active position, registration control means positionable by said selection members for operation by said actuating means to effect registration of values in said registers;

a power-operated means selectively operable to restore said selection members and said registration control means to the inactive position when displaced therefrom; and

a value-entering mechanism for controlling the differential adjustment of said section selection members;

the combination comprising:

a keyboard including a framework;

a series of depressible value keys slidably supported in each of a plurality of ordinal rows in said framework;

a power means operable to move each of said selection members from the normally inactive to a differential active position determined by a depressed value key;

an ordinal latching means normally operative to retain said selection members in the inactive position and releasable to enable operation of said power means;

means actuated by a selectively depressed value key in each row of keys operable to release the corresponding one of said latching means and to prevent depression of a value key other than the depressed key in the corresponding row of keys; and

said latching means being effective to retain a selectively depressed value key in depressed position following operation of said actuated means and the differential adjustment of the corresponding one of said selection members and restorable to normal latching position upon operation of said power-operated means.

2. In a device of the character described in claim 1 wherein said actuated means comprises:

a series of slides, one for each ordinal row of value keys movable from a normally inactive to an active position;

resilient means biasing each of said slides to the inactive position;

an interponent means associated with each of said value keys in each ordinal row of keys operable upon depression of a selected value key to move the corresponding one of said slides to the active position to release the corresponding ordinal latching means; and

each of said interponent means associated with a given row of value keys being operative upon depression of a selected key and the movement of the corresponding ordinal slide to retain the key depressed and to prevent depression of the other of said keys.

3. In a device of the character described in claim 2 wherein said interponent means comprises a bail associated with each of said value keys rockably support in said framework and rendered operable by a selectively depressed key to control movement of the corresponding ordinal slide.

4. In a device of the character described in claim 3 wherein each of said value keys is provided with a tooth projection operable upon depression of a key to rock the corresponding bail.

5. in a device of the character described in claim 4 wherein each of said bails in each ordinal row of keys is formed with one arm engaging the corresponding one of said slides and a second arm of circular configuration is provided with a notch in the periphery thereof for engagement by the tooth projection of the corresponding key upon depression thereof to rock said bail moving said one of said slides to the active position whereby the key is retained depressed and depression of the other keys in the corresponding row of keys is prevented.

6. In a device of the character described in claim 2 wherein each of said latching means comprises:

a latch member associated with a corresponding one of said selection members normally angularly disposed to the plane of adjustment of said selection member and rockable into said plane to enable operation of said power means;

an actuator means for each latch member adjustable by the depression of a key and the movement of the corresponding one of said slides to rock said latch member thereby enabling operation of said power means; and

said actuator means being effective to disable said resilient means.

7. In a device of the character described in claim 2 wherein said ordinal latching means comprises:

a latch plate associated with a corresponding one of said selection members supported in said framework adjacent said selection member and rockable from a normal latching position in a plane parallel to the plane of adjustment of said member;

said latch plate having an elongated slot therein one end portion of which is angularly extended;

a roller carried by each of said selection members adapted for movement in said elongated slot and operable in the latching position of said latch plate to engage in the angular extended end portion of the slot whereby said selection member is latched against movement; and

a latch control means for each of said latch plates normally operable to maintain said latch plate in the normal latching position and actuatable by a corresponding one of said slides to rock said latch plate upon selective depression of a value key thereby enabling movement of said roller in said elongated slot for a differential adjustment of said selection member by said power means.

8. In a device of the character described in claim 7 wherein said power means comprises a spring, one for each of said selection members.

9. in a device of the character described in claim 7 wherein said latch control means comprises a toggle linkage.

M). In a device of the character described in claim 9 wherein said toggle linkage comprises:

a lever rockable by a corresponding one of said slides upon movement thereof to the active position; and

a link having a pivotal connection with said lever normally operable jointly to retain the associated one of said latch plates in the normal latching position and effective to rock said latch plate releasing the corresponding selection member upon selective depression of a value key and and the rocking of said lever by the corresponding one of said slides. 

1. In a postage meter having a plurality of registers and an actuating means therefore: a plurality of value selection members ordinally arranged and differentially adjustable from a normally inactive to an active position, registration control means positionable by said selection members for operation by said actuating means to effect registration of values in said registers; a power-operated means selectively operable to restore said selection members and said registration control means to the inactive position when displaced therefrom; and a value-entering mechanism for controlling the differential adjustment of said section selection members; the combination comprising: a keyboard including a Framework; a series of depressible value keys slidably supported in each of a plurality of ordinal rows in said framework; a power means operable to move each of said selection members from the normally inactive to a differential active position determined by a depressed value key; an ordinal latching means normally operative to retain said selection members in the inactive position and releasable to enable operation of said power means; means actuated by a selectively depressed value key in each row of keys operable to release the corresponding one of said latching means and to prevent depression of a value key other than the depressed key in the corresponding row of keys; and said latching means being effective to retain a selectively depressed value key in depressed position following operation of said actuated means and the differential adjustment of the corresponding one of said selection members and restorable to normal latching position upon operation of said power-operated means.
 2. In a device of the character described in claim 1 wherein said actuated means comprises: a series of slides, one for each ordinal row of value keys movable from a normally inactive to an active position; resilient means biasing each of said slides to the inactive position; an interponent means associated with each of said value keys in each ordinal row of keys operable upon depression of a selected value key to move the corresponding one of said slides to the active position to release the corresponding ordinal latching means; and each of said interponent means associated with a given row of value keys being operative upon depression of a selected key and the movement of the corresponding ordinal slide to retain the key depressed and to prevent depression of the other of said keys.
 3. In a device of the character described in claim 2 wherein said interponent means comprises a bail associated with each of said value keys rockably support in said framework and rendered operable by a selectively depressed key to control movement of the corresponding ordinal slide.
 4. In a device of the character described in claim 3 wherein each of said value keys is provided with a tooth projection operable upon depression of a key to rock the corresponding bail.
 5. In a device of the character described in claim 4 wherein each of said bails in each ordinal row of keys is formed with one arm engaging the corresponding one of said slides and a second arm of circular configuration is provided with a notch in the periphery thereof for engagement by the tooth projection of the corresponding key upon depression thereof to rock said bail moving said one of said slides to the active position whereby the key is retained depressed and depression of the other keys in the corresponding row of keys is prevented.
 6. In a device of the character described in claim 2 wherein each of said latching means comprises: a latch member associated with a corresponding one of said selection members normally angularly disposed to the plane of adjustment of said selection member and rockable into said plane to enable operation of said power means; an actuator means for each latch member adjustable by the depression of a key and the movement of the corresponding one of said slides to rock said latch member thereby enabling operation of said power means; and said actuator means being effective to disable said resilient means.
 7. In a device of the character described in claim 2 wherein said ordinal latching means comprises: a latch plate associated with a corresponding one of said selection members supported in said framework adjacent said selection member and rockable from a normal latching position in a plane parallel to the plane of adjustment of said member; said latch plate having an elongated slot therein one end portion of which is angularly extended; a roller carried by each of said selection members adapted for movemeNt in said elongated slot and operable in the latching position of said latch plate to engage in the angular extended end portion of the slot whereby said selection member is latched against movement; and a latch control means for each of said latch plates normally operable to maintain said latch plate in the normal latching position and actuatable by a corresponding one of said slides to rock said latch plate upon selective depression of a value key thereby enabling movement of said roller in said elongated slot for a differential adjustment of said selection member by said power means.
 8. In a device of the character described in claim 7 wherein said power means comprises a spring, one for each of said selection members.
 9. In a device of the character described in claim 7 wherein said latch control means comprises a toggle linkage.
 10. In a device of the character described in claim 9 wherein said toggle linkage comprises: a lever rockable by a corresponding one of said slides upon movement thereof to the active position; and a link having a pivotal connection with said lever normally operable jointly to retain the associated one of said latch plates in the normal latching position and effective to rock said latch plate releasing the corresponding selection member upon selective depression of a value key and and the rocking of said lever by the corresponding one of said slides. 